Studies on the Complement Receptor of a Human Lymphoblastoid Cell Line

A human lymphoblastoid cell line, 8866, was used to investigate a surface marker, the C3d receptor. A method for cloning these cells at a relatively high efficiency was developed and C3d receptor bearing (CR+) and receptor free (CR-) subclones isolated. Receptor bearing cells were identified by their capacity to bind to complement coated sheep erythrocytes. Of the many clones isolated, only a few contained uniformly receptor positive or negative cells. Most expressed an intermediate character, not only in the percentage of CR+ cells, but also in the degree of resettability of the individual CR+ cells. Clones initially wholly CR+ remained CR+ both on prolonged culture and on recloning. CR-populatons always developed some CR+ cells with continued culture. Upon recloning, CR- clones gave rise to largely CR- clones, but also to CR+ clones, and to clones of intermediate character. Recloning of a CR+ clone derived from a CR- clone yielded mainly intermediate clones, but also CR- clones: the CR+ trait was unstable in such derivatives. Having thus demonstrated the phenotypic stability of some clones, and the instability of others, attempts were made to induce or repress the expression of the receptor. A variety of compounds (BrdU, DMSO, 2-deoxyglucose and sodium butyrate) had no effect. Neither did mixing CR+ and CRcells, nor growing CR- cells in medium conditioned by CR+ cells. There was an apparent increase in the number of CR- clones produced by the picked single cell cloning method (in which cells grow for some time at suboptimal cell densities), and CR+ cells always appeared in cultures of cells kept at optimal density in the logarithmic phase of growth. These were the only conditions found to modify the expression of the receptor